There have been known a production method of carboxylic acid ester from a carboxylic acid and an alcohol using a protonic acid catalyst. A production method using sulfuric acid as a catalyst is disclosed (Japanese Patent Laid-Open Publication No. 9-188649), and also disclosed is a method of using p-toluenesulfonic acid as a catalyst (Japanese Patent Laid-Open Publication No. 11-228491).
However, the methods using mineral acid or organic acid having strong acidity cause significant coloring due to a side reaction, which has made these methods not necessarily efficient as industrial production methods.